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Lett."],"published-print":{"date-parts":[[2026,8,1]]},"abstract":"<jats:p>Terahertz (THz) in-line digital holography is a powerful full-field phase imaging technique with a simple optical configuration and a high-space-bandwidth product. However, the phase reconstructed via conventional methods is usually wrapped in the range from \u2212\u03c0 to \u03c0. This introduces phase ambiguity, as some constraints of phase retrieval are ineffective for the wrapped phase. In this work, we propose a projected refractive-index-based phase retrieval algorithm, termed PRI-PR, to reconstruct an unwrapped phase distribution. PRI-PR avoids phase wrapping during the reconstruction by reformulating the phase retrieval problem with the projected refractive index function as the unknown, rather than the transmittance function. Meanwhile, we incorporate physical constraints, Plug-and-Play, and sparsity priors to ensure high-quality imaging for large-phase objects. 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All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.","name":"copyright","label":"Copyright"}]}}